As data rates increase in wireless communication networks and handsets, the power amplifier (PA) headroom demands placed on transmitters also tends to increase, which decreases overall transmitter efficiency. The effect is a reduction in talk or packet connect times and an increase in operating temperature. The PA headroom is a measure of the power margin available for producing higher levels of RMS output power for a given reference signal or transmitter configuration, and/or for amplifying signals having a higher peak-to-average power ratio (PAR) at a maximum rated RMS power level.
The PA consumes the largest portion of battery power in wireless handsets/devices when operating at or near maximum output power. As wireless data rates increase, handsets/devices will increasingly operate at higher output power levels, further exacerbating thermal and current drain related issues.
U.S. Pat. No. 6,281,748 describes adjusting power amplifier (PA) load impedance based on the modulation/Radio Access Technology (RAT) domain. U.S. Patent Nos. 6,160,449 and 6,166,598, both assigned to Motorola Inc., describe feedback systems where the power amplifier (PA) load impedance or power supply voltage are adjusted based on a peak-to-average power ratio (PAR) metric measured at the PA output.
In a disclosure by Motorola Inc. to the Technical Specification Group Radio Access Network (TSG RAN), R1-040642 on May. 10-14, 2004, a new cubic metric was proposed for evaluating the effect of candidate 3GPP signal configurations on power amplifier (PA) de-rating. Quantitative data suggests that the new cubic metric is a more effective predictor of power de-rating than the peak-to-average ratio (PAR) for at least some signal configurations.
The various aspects, features and advantages of the disclosure will become more fully apparent to those having ordinary skill in the art upon careful consideration of the following Detailed Description thereof with the accompanying drawings described below.